Wire sifting screen



Aug. 25, 1936. RHERMANN 2 052, 67"

WIRE SIFTING SCREEN Filed Sept. 21, 1933 1 INVENTOR ATTORNEY Patented Aug. 25, 1936 WIRE SIFTING SCREEN Rudolf Hermann, Dresden, Germany Application September 21, 1933, Serial No. 690,309 In Germany December 30, 1931' 2 Claims. (01. 209-401) This invention relates to improvements in wire sifting screens.

Attempts have been made to make screens composed of longitudinal wires only-forming openings consisting of long slits. The advantage of such a structure is, primarily, the greater open area obtained with wire as compared with shaped bars. Obviously, by using thin wires a greater open area can be obtained and a much greater capacity. or output would be attained. Furthermore, wire screens are lighter and more convenient to handle than such screens made of shaped are. I

In such attempts to make wire screens, smooth wires were placed under the greatest possible tension-in order to avoid their moving in any direction perpendicular to the wireand thus to avoid inexact screening due to lateral movements of the wires. To place such wires under the greatest possible tension, as aforesaid, the wires at one end weresecured rigidly to the frame, while the other .end was secured to a peg to which a tensioning screw was attached-similar to the tensioning device of a piano stringr It is obvious that such an arrangement is complicated and expensive; that the tension obtained is insufficient for screening operations with smooth wires, and that adjustments would often be required- To avoid individual tensioning of each wire, it is therefore suggested to secure the ends of the wires to twoparallel members and to apply tension to pull these in opposite directions. It would seem that a single tensioning member is all that is needed, but as it is not possible to have all wires of exactly the same length, the tensioning is therefore not uniform on all wires.

In view of the difficulties encountered, all commercially practical wire screen structures of the type under consideration have heretofore been made with square and oblong sieving or sifting openings, but the elongation of these sifting openings have, in order to produce practical screens with an eifective and accurate sifting or screening structure, heretofore been greatly limited in length. This limitation is due to the fact that in all the structures heretofore made, when the length of the openings have been increased beyond a given critical length for a given size of wire, it has been impossible to prevent such lateral movement of the wires as to cause inaccurate or inexact screening, sifting or sorting of the material being screened, and this difficulty has always heretofore arisen notwithstanding the fact that longitudinal wires of such screens have been placed under the greatest possible tension in at- 'bars, and it is one of the objects of my invention to provide in a wire screen such sifting slits or openings of increased and preferably greatly increased length without sacrificing accuracy or inexactness of the screening.

I accomplish this object by utilizing preformed crimped wires and producing therewith a screen panel or panels in which I employ as the side walls of increased sifting openings longitudinal wires k having a multiplicity of crimps which are not engaged by cross-wires and are so arranged as to permit free or independent vibration of said multiple-crimped portions in a plane perpendicular to the normal plane of the entire screen when in stationary position. While crimped wires have heretofore been used in screens, the crimpings of such wires have heretofore been employed in combination with cross-wires extending over and beneath either each of the crimped portions or over and beneath every second or third of the longitudinal crimps in such a manner as to destroy the aforesaid free perpendicular vibration of the crimped longitudinal wires, and such crimped Wires have heretofore principally been employed to provide a fiat woven screen structure comprising cross-wires and longitudinal wires either equally spaced apart or having cross-wires spaced to permit one or two longitudinal crimps to be unengaged by such cross-wires and thus, as aforesaid, to destroy the independent vibration of the longitudinal crimped portions which bound the openings and to provide either a rigid screen structure or one in which the cross-wires move to substantially the same extent as the longitudinal crimped portions.

In accordance with my invention, I provide longitudinal wire portions having a multiplicity of pairs of free and independent vibratory crimps and I find that such free crimped portions will not move or shift laterally to cause inaccurate or inexact screening but that such independent vibratory movements of the'multiple crimped portion in the plane of the crimps or perpendicular to the normal plane of the entire screen will improve the screening function, and I am thus enabled to produce a wire screen structure of much greater capacity and output than would be possible with smooth straight wires or with the rigidly arranged crimped and cross-wires as hereinabove described.

It will be understood that when it is attempted to simultaneously tension a series of straight, smooth wires, such wires, which are necessarily of unequal or varying lengths, will be unequally tensioned because when a similar amount of tension is applied to wires of unequal length, the shorter wires will be subjected to the greater tension and vice versa, and consequently it has heretofore been common to tension such wires individually in order to procure the closest possible uniformity of the tension on all the wires, and it is another object of my invention to enable equal or uniform tensioning of my longitudinal independently-vibratory crimped screen wires by the conventional tensioning devices and also to enable the tensioning simultaneously of all or a series of said wires instead of the usual individual tensioning thereof.

I find that when independently-vibratory crimped-wire portions are employed in a screen, substantially equal tension may be applied simultaneously and that a more uniform distribution of the tensioning throughout the length of the wire may be accomplished than is possible with smooth wire or with rigidly-mounted crimped wire and that the crimping of such wires can be employed to compensate for the inequality 1n the lengths of the wires.

Still another object of my invention is to produce a screen structure of the character described comprising a series of longitudinal wires uniformly crimped in combination with a crosswire or cross-wires arranged to provide a plu rality or series of panels composed of longitudinalwire-portions each having a multiplicity of independently-vibratory crimps toprovide openings of a length and cross-wires spaced to provide a r greatly decreased amount of dead metal in a crimped-wire screen, and a relatively large percentage of open-space in a given wire screen amounting to 85 percent and a decrease in the number of openings per square foot. In the preferred embodiment of my invention, I provide a plurality or series of cross-wires positioned close together to occupy a minimum space and to engage a minimum number of longitudinal crimps and to bound panels of unobstructed wire portions having a relatively large number of free and independently-vibratory crimps.

With these and other objects in view, the invention comprises the combination of members and arrangement of parts so combined as to co-act and cooperate with each other in the performance of the functions and the accomplishment of the results herein contemplated, and comprises in one of its adaptations the species or preferred form illustrated in the accompanying drawing, in which:--

Fig. l is a view in perspective of a harp screen embodying my invention and showing panels of wire having free crimps bounded by cross-wires positioned closely together;

Fig. 2 is a view in perspective of a fragmentary portion of a'screen showing a panel similar to those shown in Fig. 1 but having cross-wires conveniently spaced from each other;

Fig. 3 is a view in perspective of a harp screen composed of a single panel formed of longitudinal wires having free crimps;

Fig. 3a is a fragmentary longitudinal section showing a screen frame and one method of fastening and tensioning the wires;

Figs. 4 and 5 are views of a section of crimped wire disposed in comparative relationship with a series of smooth wire to show the provision made for length variations in crimped wire.

Referring now to this drawing which illustrates a preferred embodiment of my invention, S indicates a screen composed of a series of crimped wires I which are disposed longitudinally and connected at their opposite ends to suitable fastening or anchoring members 2, 2 to produce a crimped-wire panel embodying a series of crimped wires, each having a series or multiplicity of crest and trough portions free and unengaged by crosswires and which will have independent vibratory movements in the plane of the crimps or perpendicular to the plane of the screen body. These longitudinal wires I may be tensioned in any suitable manner and as illustrated in Fig. 3, I preferably provide means for applying tension simultaneously to all or a plurality or series of said longitudinal Wires. Any convenient means may be employed for applying tension to the fastening or anchoring members 2 and 2' for the purpose of tensioning said wires I, and as illustrated in Fig. 3a the screen structure is mounted in a suitable frame 3 comprising, as shown, side channel bars 30, and end channel bars 3b. Said frame may also, as shown, include members 30 and 3e of wood.

It will be understood that the screen structure may be mounted and tensioned in any conventional way and in the embodiment shown, the opposite ends of the longitudinal wires are fastened to anchor bars 2, 2' having edge portions folded beneath the screen to provide hook-shaped edges 2a and these folded edge portions 2a are connected to and tension applied in opposite directions by a plurality of threaded members 2b having outer threaded ends 20 extending through aperture 3d in the members 3e and provided with nuts 2d at such outer ends, whereby tension may be applied through said threaded members to the anchor bars 2, 2' and through them the tension may be uniformly distributed on the longitudinal wires I.

It will be seen that I employ longitudinal wires I having, as illustrated, a multiplicity of free double crimps la which vibrate independently as a panel unit. The free and vibratory crimped portions la of said wires compensate for any variation in the length of the longitudinal wires I and will enable tension to be applied to a plurality or series of such longitudinal wires simultaneously, thus avoiding and overcoming the difficulty encountered when it is attempted to tension uniformly a series of straight or smooth wires which are necessarily of unequal or varying lengths. When such wires are at each end anchored to a single fastening bar and tension is applied to said bars, the wires will be unequally tensioned, as it is apparent that when a similar amount of tension is applied to smooth wires of unequal length, the shorter wires will be subjected to the greater tension and vice versa. By utilizing wires with a multiplicity of vibratory free crimps, so mounted as to permit vibration independent of the holder members, however, I make it possible to apply uniform tension to the wires and for this purpose to utilize a single anchor 0r fastening bar for a plurality or series of longitudinal wires, thus eliminating and avoiding the conventional method of individually tensioning smooth wires, which provides independent fastening pegs for each wire.

In accordance with my invention, each screen will be composed of one, and preferably a plurality or series of screen panels 4, each of which panels is composed of wire portions having a multiplicity of vibratory free or unengaged crimps mounted to vibrate independently of cross or holder wires. I have found that by so crimping the panel portions and leaving a multiplicity or a suflicient number of crimps free and unengaged by cross-wires as to permit independent vibration of such multiple-crimped portions, I am enabled to greatly increase the length of the screen ing or sifting openings, and to change the operation of the screen. Screen panels of greatly increased length are thus provided which are unobstructed by cross-wires and these panels are preferably bounded by suitable holder members which may comprise either frame sections or cross-wires, and in Fig. 1, I have shown a screen structure comprising a series of five panels, each having a multiplicity of vibratory free crimps bounded by cross-wires anchors or holder members 5 which are positioned closely together so as to occupy a minimum space and to have no screening function but merely to function as an anchor or holder element for the longitudinal wires.

In Fig. 2 I have shown a panel bounded by anchor or holder members 5' comprising a series of crimped cross-wires interwoven at opposite ends of the panel with short sections of the longitudinal wires in the conventional manner to provide a series of square screening openings. Such anchor or holder members 5' also function in combination with the longitudinal-wire sections which they cross as screening or shifting elements. The panel sections, however, as aforesaid, comprise wire portions provided with a multiplicity of vibratory free crimps, and in Fig. 3 I have shown a screen panel similarly composed of longitudinal with a multiplicity of vibratory free crimped portions connected at opposite ends to anchor bars or holder members 2 which function as holders and fastening elements for said crimped longitudinal wires.

By utilizing such longitudinal wires having a multiplicity of vibratory free crimps, I am enabled to produce a series of effective screening panels having unobstructed screen or sifting openings of increased length, each provided with a multiplicity of such free vibratory crimps and that the panel wires will have vibratory movement independently of the holder wires and of the other panels and that such wires will not move laterally to destroy accuracy or exactness of the screening or sifting function but will vibrate in planes perpendicular to the screen body while maintaining their true positions against lateral movement; that each of such crimps may be any suitable size or are which will sufficiently reinforce and stiffen said wires to prevent such moving or shifting laterally as would cause inexact or inaccurate screening and which will permit such independent vibratory movements perpendicularly to the normal plane of the entire screen or in the plane of the crimps.

It will also be understood that by the use of my invention hereinabove described, I am enabled to provide a screen structure in which each of the said crimped-wire independently vibratory panels will be so elongated as to embody approximately twelve or more unengaged crimps and in the preferred embodiment of my invention, I provide holder members which comprise a plurality or series of cross-wires positioned close together so as to occupy a minimum space and to engage a minimum number of longitudinal crimps, thus still further increasing the length of the independently vibratory panels of unobstructed wire portions and increasing the number of free and unobstructed crimps in a panel.

It will be seen also that the number of free and unengaged crimps in a panel greatly exceeds the number of crimps engaged by holder members or cross-wires and that in Fig. 1, the number of such free unengaged crimps is approximately twelve times the number of the crimps engaged by holder members or cross-wires.

Having described my invention, I claim:--

1. A screen embodying a frame and a screening surface, comprising a screen panel mounted in said frame to produce a screening surface and comprising a series of longitudinal wires fixedly secured at one end to said frame and provided with free wire portions having crimps disposed at substantially right angles to the plane of the screening surface, and means connected to the other end of said wires for simultaneously tensioning all said longitudinal wires, whereby a. tension reserve is provided and uniform tension may be applied throughout the width of the screen panel.

2. A screen embodying a frame and a screening surface comprising a series of longitudinal crimped wires fixedly secured at one end to said frame and cross wires arranged at predetermined positions along the length of said longitudinal crimped wires to provide a screening surface composed of a plurality of screen sections, each comprising a series of longitudinal free wire portions provided with crimps disposed at substantially right angles to the plane of the screening surface, and means for simultaneously tensioning all said longitudinal wires, whereby a tension reserve is provided and uniform tension may be applied throughout the width of the screen sections.

RUDOLF HERMANN. 

